Monodentate Amine Research Articles

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Palladium(II) complexes assembled on solid materials: as catalysts for the –NO2 (nitro) to –NH2 (amine) reactions

Herein, a new series of [PdCl2(L)2] complexes where ligands are monodentate amine ligands bearing sulfonamide groups were synthesized, characterized using various techniques such as NMR, FT-IR, UV–Vis, and sc-XRD and investigated for their catalytic performance for the reduction of nitroarenes (2-nitroaniline, 4-nitroaniline, and nitrobenzene) in the presence of NaBH4 in water under heterogeneous conditions. Because the results show that the synthesized complexes are very efficient catalysts, materials using the selected palladium(II) complex supported by multiwall carbon nanotubes, silicon dioxide, and iron(II,III) oxide (Fe3O4) were fabricated by a simple-impregnation methodology, characterized by FT-IR, BET, TEM, and XRD techniques and investigated for their catalytic performance for the same reaction. Thus, a series of supported catalysts was designed with the aim of both enhancing catalytic activity and reducing noble-metal contents. Our findings serve to develop simple catalytic systems and this system can be easily used for catalytic reduction reactions which are the cornerstone of the production of important chemicals.

Effect of dithiocarbamate chelate ligands on the optical properties of InP/ZnS quantum dots and their display devices

The optical properties of colloidal quantum dots (QDs), which show unique luminescent properties in comparison with bulk materials, are generally dependent on the size of the core and shell of the QD, but are also significantly affected by ligands attached to the QD's surface. In this study, we investigated not only the effect of ligand substitution on the optical properties of the QD itself but also the QD-light emitting diode (QD-LED) in which the QD was embeded as a light-emitting material. The monodentate amine ligands of InP/ZnS QDs were replaced by bidentate dithiocarbamate (DTC) chelate ligands capable of imparting delocalization property to the surface of InP/ZnS QDs. 1H NMR spectrum showed that the native ligands were partially exchanged with the DTC ligands. Photoluminescence (PL) spectra before and after ligand substitution show a bathochromic shift of about 10–25 nm depending on the electrical resonant properties of the DTC ligands. The QD-LED device was fabricated using QDs replaced by DTC ligands, and some improvements in device properties were observed. Here, we first report the ligand dependence of the photo- and the electroluminescence of InP/ZnS QDs in solution and device.

Energy level tuning of InP/ZnS nanocrystals by electronically delocalized dithiocarbamate derivatives

The nanocrystals have characteristics of varying the energy gap between the valence band and the conduction band depending on the size, and are attracting attention as light emitting materials due to the excellent in light stability. Since the bandgap of nanocrystals is determined by the size, it is very important to control the size of the nanocrystals in order to realize the red, green and blue primary color in a display. However, there are many difficulties in finely adjusting the nanocrystal bandgap to a size. In this study, the monodentate amine ligands coordinated on the surface of InP/ZnS nanocrystals are substituted with bidentate dithiocarbamate ligands having a strong coordination ability and electrically resonant structures, so that the nanocrystal can be finely tuned to control the emission spectrum. NMR analysis showed that some amine ligands on the surface of the nanocrystals were substituted with dithiocarbamate ligands. The PL spectra also show that the emission wavelength of the new nanocrystals is increased by about 20 nm (bathochromic shift), indicating that the active region of the exciton (an electron-hole pair) is extended to the delocalized dithiocarbamate ligands as well as the nanocrystals.

Covalently functionalized amide cross-linked hydrogels from primary amines and polyethylene glycol acyltrifluoroborates (PEG-KATs).

A new method for the rapid preparation of chemically cross-linked hydrogels based on a multi-arm polyethylene glycol (PEG) bearing potassium acyl trifluoroborate (KAT) functional groups with multi-dentate amines is described. These scaffolds - prepared in aqueous buffer - give strong, transparent hydrogels. At pH 3, the gel formation is complete within seconds, and the reaction rate can be tuned by modulating the pH. Rheology measurements show that the hydrogel properties can be tuned as a function of both the weight percent of solids in the gel and the denticity of amine cross-linker, allowing for predictable formation of gels with desired traits. This process relies on a rapid amide-forming reaction of KATs and in situ generated N-chloroamines. Numerous commercially available amines, including di-, tri- and tetra-functional amines as well as peptides and carbohydrates serve as effective cross-linkers. Monodentate amines included in the gelation mixture are covalently linked into the gel matrix by amide-bonds, allowing gels containing immobilized molecules including dyes, sensors, or biotin amine, to be prepared in a single step from simple starting materials. The ability to induce gelation only upon addition of equimolar amounts of an inexpensive inducer (N-chlorosuccinimide) allows premixed components to be stored as an aqueous solution for weeks and converted to gels on demand.

Easy To Synthesize, Robust Organo-osmium Asymmetric Transfer Hydrogenation Catalysts.

Asymmetric transfer hydrogenation (ATH) is an important process in organic synthesis for which the Noyori‐type RuII catalysts [(arene)Ru(Tsdiamine)] are now well established and widely used. We now demonstrate for the first time the catalytic activity of the osmium analogues. X‐ray crystal structures of the 16‐electron OsII catalysts are almost identical to those of RuII. Intriguingly the precursor complex was isolated as a dichlorido complex with a monodentate amine ligand. The OsII catalysts are readily synthesised (within 1 h) and exhibit excellent enantioselectivity in ATH reactions of ketones.

The first diperoxidovanadium complex with a monodentate amine ligand: Synthesis, characterization and crystal structure of methylbenzylammonium oxido-diperoxido-methylbenzylaminevanadate monohydrate

The synthesis and structure of the first vanadium diperoxido complex carrying a monodentate amine ligand coordinated solely through its –NH2 group is reported herein. (S)-methylbenzylamine (mba) is acting as a ligand, while its protonated form is the cation in mbaH[VO(O2)2(mba)]∙H2O (1), which was isolated from a solution obtained by dissolving vanadium pentoxide in high excess of the amine and adding HCl and H2O2. [VO(O2)2(mba)]− is the dominating species in this solution and shows a resonance at −732ppm in 51V NMR spectrum. The anion exhibits in infrared and Raman spectra bands typical for pentagonal pyramidal diperoxido complexes of vanadium. The band assignment of the characteristic vibrations was confirmed by DFT calculations.

Toward molecular recognition: three-point halogen bonding in the solid state and in solution.

A well-defined three-point interaction based solely on halogen bonding is presented. X-ray structural analyses of tridentate halogen bond donors (halogen-based Lewis acids) with a carefully chosen triamine illustrate the ideal geometric fit of the Lewis acidic axes of the former with the Lewis basic centers of the latter. Titration experiments reveal that the corresponding binding constant is about 3 orders of magnitude higher than that with a comparable monodentate amine. Other, less perfectly fitting multidentate amines also bind markedly weaker. Multipoint interactions like the one presented herein are the basis of molecular recognition, and we expect this principle to further establish halogen bonding as a reliable tool for solution-phase applications.

Poly[bis(μ-2-amino-4-nitrobenzoato)di-μ-aqua-dirubidium

In the structure of the title salt, [Rb2(C7H5N2O4)2(H2O)2]n, the asymmetric unit comprises two independent and different seven-coordinate Rb+ cations, one forming an RbO7 polyhedron, the other a RbO6N polyhedron, each of which is considerably distorted. The RbO7 polyhedron comprises bridging O-atom donors from two water mol­ecules, three carboxyl­ate groups, and two nitro groups. The RbO6N polyhedron comprises the two bridging water mol­ecules, one monodentate amine N-atom donor, one carboxyl O-atom donor and three O-atom donors from nitro groups (one from the chelate bridge). The extension of the dinuclear unit gives a three-dimensional polymeric structure which is stabilized by both intra- and inter­molecular amine N—H⋯O and water O—H⋯O hydrogen bonds to carboxyl and water O-atom acceptors, as well as a number of inter-ring π–π inter­actions [minimum centroid–centroid separation = 3.364 (2) Å]. The title salt is isostructural with the analogous caesium salt.

Supramolecular assemblies of Ru(ii) organometallic half-sandwich complexes

Extended hydrogen bonding network in [(arene)Ru(para-substituted amine ligand)Cl2].

Silver‐Containing Ionic Liquids with Alkylamine Ligands

AbstractThe synthesis, structure and electrochemical properties of several silver‐containing liquid metal salts have been investigated. These ionic liquids comprise of a silver‐containing cation with a silver centre coordinated by two or more alkylamine ligands and a bis(trifluoromethylsulfonyl)imide (Tf2N) anion. With the monodentate amines tert‐butylamine (tBuAm), iso‐butylamine (iso‐BuAm), sec‐butylamine (sec‐BuAm), 2‐ethylhexylamine (2‐EtHexAm), di(2‐ethylhexyl)amine and piperidine (pip), compounds with the formula [Ag(L)2][Tf2N] are formed, several of which are room‐temperature ionic liquids and all melt at or below 100 °C. In the case of [Ag(L)2][Tf2N] (L=tBuAm, iso‐BuAm and pip), single‐crystal X‐ray diffraction shows that, in the solid state, the silver centres are two‐fold coordinated by two amine ligands and the anion and cation exist as separated ion pairs. With ethylenediamine (en), two different compounds were formed, depending on the silver‐to‐ligand ratio and their structures were elucidated by X‐ray diffraction. [Ag(en)][Tf2N] has a very high melting point and is polymeric in the solid state, with en ligands coordinated to different silver(I) centres, creating one‐dimensional chains. [Ag(en)2][Tf2N], on the other hand, is a room‐temperature ionic liquid, with four‐coordinate silver(I) centres, but is actually polymeric in the solid state. The electrodeposition behaviour of [Ag(2‐EtHexAm)2][Tf2N] and [Ag(en)2][Tf2N] was investigated both at room temperature and at 90 °C and it was possible to achieve very high current densities in unstirred solutions and to electrodeposit closed, crack‐free, silver coatings. A crystal of [Ag2(en)Cl2] was obtained from a solution of [Ag(en)][Tf2N] in deuterochloroform and its structure is described.

A Chiral Decorated Metal–Isonicotinate Coordination Polymer

The isostructural coordination polymers, M(isonicotinate)(tyrosinate)(H2O)2 [M = Co or Ni] have been synthesized by microwave-assisted hydrothermal methods. These compounds crystallize in the non-centric space group P21. At 290 K, for the cobalt analogue the unit cell parameters are a = 6.0658(6), b = 15.540(2), c = 9.1328(9) A, β = 107.052(7)°, V = 823.05(16) A3; for the nickel compound a = 6.0946(8), b = 15.443(2), c = 9.1202(11) A, β = 107.803(10)°, V = 817.28(19) A3. The structure contains linear chains with composition [M(isonicotinate)]∞ in which the isonicotinate is arranged head-to-tail and binds to octahedral cations through both pyridine and monodentate carboxylate functions. At each metal centre the coordination is completed by two cis water molecules and tyrosinate that chelates to the metal centre through monodentate carboxylate and amine groups. The chains run parallel to the crystallographic [101] direction. Between the chains there is extensive hydrogen bonding between bound water and carboxylate groups. The cobalt compound loses water upon heating above room temperature and continues to lose mass in ill-defined steps upon further heating; in contrast the nickel compound loses mass in well-defined steps. An achiral one dimensional chain can be decorated with the chiral auxiliary tyrosine to produce a homochiral coordination polymer.

Synthesis, and characterization of cobalt(III) complexes with Schiff bases derived from 2-hydroxynaphthaldehyde, (naph) 2dien and (naph) 2dpt, and monodentate amine ligands: Crystal structure, spectral and redox properties

Two series of complexes of the type [Co III{(naph) 2dien}(amine)]BPh 4 {(naph) 2dien = bis-(2-hydroxy-1-naphthaldimine)-N-diethylenetriamine dianion, and amine = piperidine (pprdn) ( 1), pyrrolidine (prldn) ( 2), pyridine (py) ( 3), N-methylimidazole (N-MeIm) ( 4)}, and [Co III{(naph) 2dpt}(amine)]BPh 4 {(naph) 2dpt = bis-(2-hydroxy-1-naphthaldimine)-N-dipropylenetriamine dianion, and amine = piperidine (pprdn) ( 5), 3-methylpyridine (3-Mepy) ( 6)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and 1H NMR spectroscopy. The crystal structures of ( 2) and ( 6) have been determined by X-ray diffraction. The redox potentials of the central cobalt ion show a relatively good correlation with the σ-donor ability of the axial ligands. The spectroscopic and electrochemical properties of these complexes are also influenced by the mutual steric hindrance between the pentadentate Schiff base and the ancillary ligands.

Generation and Optical Properties of Monodisperse Wurtzite-Type ZnS Microspheres

Monodisperse wurtzite-type ZnS microspheres have been prepared by using glutathione (GSH) as a sulfur source at low reaction temperatures ranging from 160 to 210 degrees C. The diameter of the ZnS microspheres can be tuned from approximately 254 to approximately 597 nm by changing the reaction parameters such as temperature, molar ratio of reactants (GSH/Zn2+), and reaction medium (ethylenediamine or ammonia). Our results demonstrate that monodentate amines (ammonia) play the same role as that of bidentate amines (ethylenediamine) in the formation of the wurtzite-type ZnS microspheres. The formation process of the monodisperse ZnS microspheres consists of a GSH-dominated nucleation process and an amine-dominated assembly process. The as-synthesized monodisperse ZnS microspheres readily self-assemble into ordered hexagonal patterns and thus have potential applications as colloidal crystalline materials. Blue fluorescence emission peaks at 415 and 466 nm in wavelength, attributed to deep-trap emission, are observed at room temperature.

Platinum Complexes with One Monodentate Ligand (1‐Methylbenzimidazole or Antiviral Ribavirin) Flanked by Two cis‐NMe2 Groups: Informative Models for Assessing Interligand Interactions

AbstractPlatinum complexes with a tridentate amine ligand (A3) and a nucleobase (L) represent very useful models for investigating nucleobase/cis‐amine interactions without the complications arising from nucleobase/nucleobase interferences present in the more frequently used cis‐A2PtL2 model systems (A2 = two monodentate amines or a diamine). In this context, the Me3dienPtL complexes (Me3dien = N1,N4,N7‐trimethyldiethylenetriamine), previously investigated, were particularly informative. The presence of a methyl group on each terminal nitrogen atom renders the rotation of L about the Pt–L bond slow on the NMR timescale and the two half spaces defined by the coordination plane inequivalent. Thus, guanine and deoxyguanine derivatives were found to have comparable rates of rotation by way of a H‐bond interaction between the O6 atom of the rotating guanine and the NH group of the cis‐amine. We have now extended the investigation to Me5dien complexes (Me5dien = N1,N1′,N4,N7,N7′‐pentamethyldiethylenetriamine). The results indicate that the absence of a proton on the terminal nitrogen atoms not only reduces the rate of rotation of L by a factor of 1010, but also dramatically increases the difference in the rates between the L ligands mimicking guanine and deoxyguanine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis, multinuclear magnetic resonance and crystal structures of Pt(II) complexes containing amines and bidentate carboxylate ligands

A novel synthetic method for the synthesis of the complexes cis-Pt(amine) 2R(COO) 2 is compared to two other methods involving the use of either barium dicarboxylate or sodium carboxylate. Pt(II) compounds with monodentate and bidentate amines were studied. The reaction involves the use of a silver dicarboxylato complex, which is the intermediate in the new synthetic procedure. The crystal structure of the silver intermediate with the ligand 1,1-cyclobutanedicarboxylate (1,1-CBDCA) was determined by X-ray diffraction. The crystal Ag 2(1,1-CBDCA) has a very interesting 3-D extended structure. The complexes cis-Pt(amine) 2R(COO) 2 were studied in solution by multinuclear ( 1H, 13C and 195Pt) magnetic resonance spectroscopy, but the solubilities are very low. D 2O was found to be the best solvent. In 195Pt NMR, the complexes containing bidentate amines forming five-membered chelates were observed at higher fields than those containing monodentate amines. The resonances of the NH 3 compounds were also found at lower fields than the primary amine complexes. All the dicarboxylato ligands form six-membered chelates except 1,2-CBDCA, whose Pt(II) compounds were observed at lower fields than the others. The crystal structures of Pt(en)(1,1-CBDCA), Pt(Meen)(1,1-CBDCA) and Pt(en)(benzylmalonato) were confirmed by X-ray diffraction methods. Several compounds are disordered. The crystals are stabilized by intermolecular hydrogen bonds between the –NH 2 groups and the carboxylato O atoms.

Properties of silicas chemically modified by monodentate amines studied by conductometry

The protonation of aminoalkyl groups covalently bonded on the silica surface was studied by the conductometric titration method. Porous varieties of silica can adsorb HCl from an aqueous solution. Conductometric titration was proposed for the determination of concentrations and constants of protolytic equilibrium of grafted amino groups. During HCl chemisorption the effect of temperature on the electric conductivity of suspensions of the modified silicas was studied.

Chelate vs monodentate amine effects. Direct comparison of bis(acetato)amminedichloro(cyclohexylamine)platinum(IV) (JM216) with its N-cyclohexyl-1,3-propanediamine analogue

In order to investigate the chelate effects on physicochemical properties including antitumor activity, new cis, trans, cis,-[Pt IVCl 2L 2(chpda)] complexes (L=OH, OCOCH 3; chpda= N-cyclohexyl-1,3-propanediamine) have been synthesized and characterized. The crystal structure of cis, trans, cis-[Pt IVCl 2(OCOCH 3) 2(chpda)] (monoclinic P2 1/ a, a=7.947(1), b=22.753(11), and c=10.581(3) Å, β=110.70(2)°, V=1790(1) Å 3, Z=4, R=0.0534) shows that the platinum(IV) center adopts a typical octahedral arrangement with two acetate groups in a trans position. The pattern and strength of the intramolecular hydrogen bonds are delicately different from those of JM216. Both in vitro and in vivo (oral) cytotoxicities on mouse leukemia L1210 cell line indicate that the activity of chpda chelate analogue is not better than that of the corresponding compound with two monodentate amines (JM216).

Synthesis and characterization of Pt(II) complexes with amine and carboxylato ligands. Crystal structure of (1,1-cyclobutanedicarboxylato)di(ethylamine)platinum(II)·H 2O

Two methods for the synthesis of compounds of the type cis-PtA 2X 2 (A 2=bidentate amine or two monodentate amines and X 2=bidentate or two monodentate carboxylato ligands) were evaluated. The compounds were characterized by multinuclear NMR and IR spectroscopies. The 195Pt NMR chemical shifts were in the range −1615 to −1976 ppm, the higher field values corresponding to the complexes containing bidentate ligands. The coupling constants 3 J( 195Pt– 1H) are approximately 35 Hz, while the 2 J( 195Pt– 1HN) are about 70 Hz. One coupling constant 2 J( 195Pt– 13C) (53 Hz) was also measured. The crystal structure of the compound, cis-Pt(1,1-cyclobutanedicarboxylato)(C 2H 5NH 2) 2·H 2O belongs to the P2 1/ n space group with a=9.468(5), b=9.365(4), c=16.473(7) Å, β=105.08(3)°, Z=4 and R 1=0.0576. The PtN bond distances are 1.992(5) and 2.020(5) Å, while the PtO bonds are 2.000(4) and 2.015(4) Å. The molecules are held together by intermolecular H-bonds involving the lattice water molecules and the two free carbonyl O atoms and between the amino H atoms and the Pt-bonded CO groups.

Syntheses and structures of novel zerovalent ruthenium monodentate amine complexes †

Novel ruthenium(0) monodentate amine (primary, secondary, and tertiary) and pyridine complexes, [Ru(η6-cot)(η2-dmfm)(L)] (cot = cycloocta-1,3,5-triene, dmfm = dimethyl fumarate; L = propylamine, benzylamine, dimethylamine, morpholine or pyridine), were prepared by the reaction of [Ru(η6-cot)(η2-dmfm)2] with the corresponding amine in high yields. The structures of three of the complexes were determined by X-ray analyses and the co-ordination geometry around the central ruthenium atom is a highly distorted trigonal bipyramid. The nitrogen atom and one carbon–carbon double bond of the cyclooctatriene occupy the two axial positions, and the other two olefinic bonds of the cyclooctatriene and dimethyl fumarate the equatorial positions. The propylamine complex is in equilibrium with [Ru(η4-cot)(η2-dmfm)(PrNH2)2] in the presence of an excess of propylamine. The structure of this complex was confirmed by X-ray analysis. The position of the second amine is equatorial and the cyclooctatriene co-ordinated in a 1–2∶5–6-η bonding mode. When it was dissolved in CD2Cl2, propylamine at the equatorial position was dissociated, changing the η4-cyclooctatriene to the η6 mode to give [Ru(η6-cot)(η2-dmfm)(PrNH2)].